Some code tweaks

app/controllers/projects/merge_requests_controller.rb

@@ -576,13 +576,10 @@ class Projects::MergeRequestsController < Projects::ApplicationController
     @comparable_diffs = @merge_request_diffs.select { |diff| diff.id < @merge_request_diff.id }
     if params[:start_sha].present?
-      @start_sha = params[:start_sha]
-      @start_version = @comparable_diffs.find { |diff| diff.head_commit_sha == @start_sha }
-      unless @start_version
-        @start_sha = @merge_request_diff.head_commit_sha
-        @start_version = @merge_request_diff
-      end
+      start_sha = params[:start_sha]
+      @start_version = @comparable_diffs.find { |diff| diff.head_commit_sha == start_sha }
+      @start_sha = start_sha if @start_version
     end
     @diffs =

app/helpers/notes_helper.rb

@@ -76,7 +76,7 @@ module NotesHelper
       diffs_namespace_project_merge_request_path(discussion.project.namespace, discussion.project, discussion.noteable, diff_id: diff_id, anchor: discussion.line_code)
     elsif discussion.for_commit?
       anchor = discussion.line_code if discussion.diff_discussion?
-      
+
       namespace_project_commit_path(discussion.project.namespace, discussion.project, discussion.noteable, anchor: anchor)
     end
   end

app/models/concerns/discussion_on_diff.rb

@@ -5,8 +5,6 @@ module DiscussionOnDiff
   included do
     NUMBER_OF_TRUNCATED_DIFF_LINES = 16
-    memoized_values << :active
-
     delegate  :line_code,
               :original_line_code,
               :diff_file,
@@ -29,12 +27,6 @@ module DiscussionOnDiff
     true
   end
-  def active?
-    return @active if @active.present?
-
-    @active = first_note.active?
-  end
-
   # Returns an array of at most 16 highlighted lines above a diff note
   def truncated_diff_lines(highlight: true)
     lines = highlight ? highlighted_diff_lines : diff_lines

app/models/concerns/note_on_diff.rb

@@ -26,6 +26,10 @@ module NoteOnDiff
     raise NotImplementedError
   end
+  def active?(diff_refs = nil)
+    raise NotImplementedError
+  end
+
   private
   def noteable_diff_refs

app/models/legacy_diff_discussion.rb

@@ -7,6 +7,8 @@
 class LegacyDiffDiscussion < Discussion
   include DiscussionOnDiff
+  memoized_values << :active
+
   def legacy_diff_discussion?
     true
   end
@@ -15,6 +17,12 @@ class LegacyDiffDiscussion < Discussion
     LegacyDiffNote
   end
+  def active?(*args)
+    return @active if @active.present?
+
+    @active = first_note.active?(*args)
+  end
+
   def collapsed?
     !active?
   end

app/views/discussions/_discussion.html.haml

@@ -30,6 +30,7 @@
               - else
                 a deleted commit
             - elsif discussion.diff_discussion?
+              on
               = conditional_link_to url.present?, url do
                 - if discussion.active?
                   the diff

app/views/projects/merge_requests/show/_versions.html.haml

@@ -72,13 +72,14 @@
         = link_to namespace_project_compare_path(@project.namespace, @project, from: @start_version.base_commit_sha, to: @merge_request_diff.base_commit_sha) do
           new commits
         from
-        %code= @merge_request.target_branch
+        = succeed '.' do
+          %code= @merge_request.target_branch
     - if @diff_notes_disabled
       .comments-disabled-notif.content-block
         = icon('info-circle')
         - if @start_sha
-          Comment creation is disabled because you're comparing two versions of this merge request.
+          Comments are disabled because you're comparing two versions of this merge request.
         - else
           Discussions on this old version of the merge request are displayed but comment creation is disabled.

spec/features/merge_requests/merge_request_versions_spec.rb

@@ -66,7 +66,7 @@ feature 'Merge Request versions', js: true, feature: true do
     end
     it 'show the message about disabled comments' do
-      expect(page).to have_content 'Comment creation is disabled'
+      expect(page).to have_content 'Comments are disabled'
     end
     it 'show diff between new and old version' do